Method and device for phase adjustment based on closed-loop diversity feedback

ABSTRACT

A mobile communications method, device, and system for adjusting a phase parameter in a diversity signal, based at least in part on phase feedback from a base station. While in uplink communication with a base station, a mobile device may receive a phase feedback signal from the base station. The mobile device may calculate a modified value of a phase parameter based on the phase feedback signal in order to transmit diversity signals with a gradual change in phase difference. The modified value may be between a phase parameter value indicated by the base station&#39;s phase feedback signal and a phase parameter value initially transmitted by the mobile device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/398,598 filed Feb. 16, 2012, now allowed, which claims benefit ofU.S. Provisional Patent Application Ser. No. 61/443,542 filed Feb. 16,2011, the entirety of which are incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates generally to the field of mobile wirelesscommunications and more specifically to adjusting phase parameters basedclosed-loop diversity feedback.

BACKGROUND OF THE INVENTION

In a mobile transmit diversity system, a base station may send diversityfeedback to a mobile communications device or mobile device in itsnetwork or vicinity. The diversity feedback may instruct the mobiledevice to transmit a diversity signal with certain diversity parameters,such as phase difference or relative power amplitude. A base station maylimit the size of its feedback to a mobile device to save downlinkbandwidth. For example, a codebook size limitation considered by the3^(rd) Generation Partnership Project (3GPP) is two bits. Such phasefeedback may only have four codebook options to direct the mobiledevice's phase: 0, +90, 180, or −90, for example. However, it isdifficult with such a coarse resolution to provide sufficientsensitivity for optimum diversity gain.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention include a method, device, and system foradjusting a phase difference between two signals, based on closed-looptransmit diversity feedback from a base station. A mobile communicationsdevice may receive transmit diversity feedback from a base station, andthe phase feedback signal may be based on a previous diversity signalreceived at the base station. The mobile device may calculate a modifiedvalue of a phase parameter based on the phase feedback signal. Themodified value may be between a phase parameter value indicated by thephase feedback signal and a phase parameter value previously transmittedby the mobile device. The mobile device may control and determinedifferent methods of calculation based on prior phase feedback signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1 is a flowchart diagram of a method of adjusting phase differencebased on closed-loop phase feedback from a base station, according to anembodiment of the present invention;

FIG. 2A is a flowchart diagram of a method of adjusting phase differencebased on comparing a current phase feedback with a prior phase feedbacksignal, according to an embodiment of the present invention;

FIG. 2B a schematic depiction of a series of closed-loop phaseadjustments, according to an embodiment of the invention; and

FIG. 3 is an illustration of a combination of control and calculationmethods for phase adjustment, according to an embodiment of theinvention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Although embodiments of the invention are not limited in this regard,the terms “plurality” and “a plurality” as used herein may include, forexample, “multiple” or “two or more”. The terms “plurality” or “aplurality” may be used throughout the specification to describe two ormore components, devices, elements, units, parameters, or the like.Unless explicitly stated, the method embodiments described herein arenot constrained to a particular order or sequence. Additionally, some ofthe described method embodiments or elements thereof can occur or beperformed simultaneously, at the same point in time, or concurrently.

The present invention may be applicable in any communication networkbetween a mobile device and a second communication device, including butnot limited to a base station. Networks may utilize communicationprotocols and technologies to provide the communication sessions.Examples of communication protocols and technologies include those setby the Institute of Electrical and Electronics Engineers, Inc. (IEEE)802.xx standards, International Telecommunications Union (ITU-T)standards, European Telecommunications Standards Institute (ETSI)standards, Internet Engineering Task Force (IETF) standards, or otherstandards.

Communication devices in a network may use any suitable multiple accesstechnology, for example, a code division multiple access (CDMA)technology. According to one embodiment, the network may operateaccording to a CDMA 2000 telecommunications technology that uses asingle CDMA channel. As an example, a CDMA 2000 high rate data packettechnology, such as the Evolution Data Optimized (EvDO) technology maybe used. Other examples of multiple access technology include wide bandCDMA and UMTS (Universal Mobile Telecommunications System). Acorresponding high data rate application such as High Speed PacketAccess (HSPA) technology may be used as well.

The network may comprise any suitable communication network. Acommunication network may comprise all or a portion of a public switchedtelephone network (PSTN), a public or private data network, a local areanetwork (LAN), a metropolitan area network (MAN), a wide area network(WAN), a global computer network such as the Internet, a wirelessnetwork, a local, regional, or global communication network, anenterprise intranet, other suitable communication link, or anycombination of the preceding.

A component of a network, for example, a mobile communication device ormobile user equipment device (mobile device), may include logic, aninterface, memory, other component, or any suitable combination of thepreceding. “Logic” may refer to hardware, software, other logic, or anysuitable combination of the preceding. Certain logic may manage theoperation of a device, and may comprise, for example, a processor.“Interface” may refer to logic of a device operable to receive input forthe device, send output from the device, perform suitable processing ofthe input or output or both, or any combination of the preceding, andmay comprise one or more ports, conversion software, or both. “Memory”may refer to logic operable to store and facilitate retrieval ofinformation, and may comprise a Random Access Memory (RAM), a Read OnlyMemory (ROM), a magnetic drive, a disk drive, a Compact Disk (CD) drive,a Digital Video Disk (DVD) drive, a removable media storage, any othersuitable data storage medium, or a combination of any of the preceding.

The communication network may include one or more mobile communicationdevices and one or more other communication devices that receive signalsfrom mobile devices and give feedback, for example, base stations thatcommunicate with a mobile device via a wireless link. A mobilecommunication device unit may comprise any device operable tocommunicate with a base station, for example, a personal digitalassistant (PDA), a cellular telephone, a mobile handset, a laptopcomputer, or any other device suitable for communicating signals to andfrom a base station. A subscriber unit may support, for example, SessionInitiation Protocol (SIP), Internet Protocol (IP), or any other suitablecommunication protocol.

A base station may provide a mobile communication device access to acommunication network that allows the subscriber unit to communicatewith other networks or devices. A base station typically includes a basetransceiver station and a base station controller. The base transceiverstation communicates signals to and from one or more subscriber units.The base station controller manages the operation of the basetransceiver station.

According to embodiments of the invention, the mobile communicationdevice may include two or more antenna elements, where each antennaelement is operable to receive, transmit, or both receive and transmit asignal. Multiple antenna elements may provide for a separation processknown as spatial filtering, which may enhance spectral efficiency,allowing for more users to be served simultaneously over a givenfrequency band. The two signals may propagate along different paths andmay reach the receiving communication device or base station withdifferent phases that constructively or destructively interfere. Two ormore signals that constructively interfere may exhibit higher diversitygain, or higher relative performance than if the sum of the two signalswere transmitted. Diversity gain may be an indicator of efficient signalperformance.

A diversity signal may include two or more signals transmittedcontemporaneously on the two or more antenna elements. Diversity signalsmay be transmitted using a diversity parameter. A diversity parametermay be a parameter or value by which the transmissions on any twoantennas differ, for example a difference in transmission phase on thetwo antennas, or a ratio of transmission power on the two antennas. Itwill be understood that although examples are provided in the presentapplication pertaining to phase difference between two antennas, theinvention is applicable using the same principles to varying anytransmit diversity parameter. Although the embodiments described in thepresent application are described as using two antennas, it will berecognized that the present invention is equally applicable to transmitdiversity systems and devices having more than two antennas.

According to embodiments of the present invention, the mobilecommunication device may include a processor and a transmit/receivemodule that calculate and produce one or more signals for transmissionover at least first and second antennas. A phase modulator may produce aphase difference between two or more signals that are transmitted on thetwo or more antennas.

The value of a transmit diversity parameter may be determined based on anumber of feedback schemes, including “open-loop” feedback, in which themobile device calculates the value based on signal quality feedbacksignals sent by the base station, which may not necessarily be dedicatedto transmit diversity, or “closed-loop” feedback, in which the mobiledevice calculates the value based on a phase correction or modificationfeedback signal sent by the base station, e.g., an explicit instructionfrom the base station to adjust or modify the value of the transmitdiversity parameter in a particular direction and/or by a particularamount.

According to embodiments of the invention, modifying a diversity signalmay refer to modifying a signal feature or a diversity parameter. Forexample, a signal may be transmitted by the two antennas using amodified signal feature, or a different value of a transmit diversityparameter than a previous value. Relative phase may refer to the phasedifference between the phase of a first signal of a first transmitantenna element and the phase of a second signal of a second transmitantenna element. Relative power may refer to the ratio between the powerof a first signal of a first transmit antenna element and the power of asecond signal of a second transmit antenna element, which ratio may bedefined on a linear or logarithmic scale. According to embodiments ofthe invention, modifying a signal may refer to adjusting, for example, anominal value of a phase feedback parameter so that two signals have adifferent relative phase than before signal modifications. Othermodifications may occur.

The quality of one or more recent uplink signals from the mobile devicemay depend on the changing geometry or position of the mobile devicewith respect to the base station and through varying propagationconditions. Accordingly, in a closed-loop feedback scheme, a basestation may send to a mobile device a transmit diversity feedbacksignal, e.g., a phase feedback signal, instructing the mobile device tomodify or set its value of the transmit diversity parameter. Forexample, an instruction may include a phase feedback parameter,commanding a mobile device to modify the diversity signal's relativephase difference. A base station may expressly instruct the mobiledevice how to modify the phase difference so as to improve reception,based on the quality of past or recent uplink signals from the mobiledevice. The transmit diversity feedback signal may be the desired value,or a differential value relative to the current value, and may be sentas the actual value, or as a code from a codebook. The mobile device mayuse the base station's instructions to determine a modified phaseparameter.

In some embodiments of the invention, a mobile network communicationstandard may limit the number of bits that are used to send diversityfeedback to the mobile device. For example, the base station's phasefeedback signal may be two bits, in order not to take up excessivebandwidth from other downlink communication signals and data. Thecombination of bit values may correspond to a value of phase difference,e.g. ‘00’ may refer to a phase parameter value of 0°, ‘01’ may refer toa phase parameter value of +90°, etc. Other phase parameter values maybe used. With a limited number of bits in the feedback signal, e.g., nbits, the base station may be limited to describing 2^(n) possiblevalues of phase parameters, e.g., for n=2, four possible values of phaseparameters may include 0°, +90°, 180°, or −90°. If strictly complyingwith the base station's instructions, the mobile device may be preventedfrom optimizing the transmission quality of its uplink diversity signaldue to the large phase step difference between the possible phaseparameters (e.g., a minimum phase step difference of 90°). According tosome embodiments, the mobile device may transmit diversity signals usingfiner phase difference resolutions and smaller phase steps betweenadjacently valued phase parameters.

In some embodiments of the invention, a base station may provideclosed-loop feedback to the mobile device by sending a transmitdiversity feedback signal, e.g. phase feedback signal, to the mobiledevice. As discussed above, such a phase feedback signal may include avalue of a phase parameter. Feedback information from the base stationmay be used to calculate a modified value of a phase parameter that is asmaller phase step towards the value of a phase parameter indicated bythe base station's phase feedback signal. According to embodiments ofthe invention, the mobile device may use beamforming to transmitdiversity signals using phase parameter values that reach the basestation's phase parameter value in a graduated manner. As describedbelow, according to embodiments of the invention, the mobile device maytransmit a diversity signal with a modified value of a phase parameterthat is between the phase value indicated by the base station's phasefeedback signal and a phase value that the mobile device is currentlyusing to transmit an initial diversity signal.

For example, in some embodiments of the invention, a mobile device mayreceive a plurality of consecutive phase feedback signals that indicatethe same value of a phase parameter. As discussed previously, a basestation may send phase feedback signals to a mobile device based on, forexample, the changing geometry or position of the mobile device withrespect to the base station. A plurality of the same consecutive phasefeedback signals sent to a mobile device may imply that the mobiledevice is unlikely to drastically change its position relative to thebase station, or that the mobile device is traveling more slowly. Insuch a case, the mobile device may determine to transmit diversitysignals at a finer phase difference resolution, so that if the basestation sends a different phase feedback signal, the mobile device maycalculate a modified value of a phase parameter that is between thephase value that the mobile device is currently using and the phasevalue indicated by the base station's phase feedback signal. The mobiledevice may transmit successive diversity signals, each with phaseparameters that differ at smaller phase steps than the phase stepsbetween adjacently valued phase feedback signals. The smaller phasesteps may mitigate against a base station's overcorrection in the phasevalue transmitted with a diversity signal. The mobile device may thuschange phase parameters more gradually or at a slower rate than the rateof change of the base station's phase feedback signals.

FIG. 1 depicts a flowchart of a method 100 by a mobile device ofadjusting phase difference based on closed-loop phase feedback from abase station, according to an embodiment of the invention.

At block 102, a mobile device may transmit an initial diversity signalto a base station using an initial value of a phase parameter. At block104, the mobile device may receive a current or recent phase feedbacksignal from a base station. The phase feedback signal sent by the basestation may be based on the quality of the mobile device's initialdiversity signal, as received at the base station. The phase feedbacksignal may contain a value of a phase parameter, which may be calculatedby the base station to increase diversity gain at the base station asexpected if the mobile device transmitted a diversity signal with thedesired value of the phase parameter.

At block 106, the mobile device may calculate a modified value of thephase parameter. The modified phase parameter value may be a gradualphase step toward the phase parameter indicated by the base station'sphase feedback signal. The modified phase parameter may be calculated,for example, by applying a small phase step to the initial phaseparameter value used by the mobile device. The modified phase parametermay have a value that is between the initial phase parameter value andthe current value indicated by the current phase feedback signalreceived in block 102.

At block 108, the mobile device may transmit a modified diversity signalusing the calculated modified value of the phase parameter.

The method may repeat blocks 104-108. Thus, for example, the modifiedvalue of the phase parameter in 108 may become the initial or firstvalue of a phase parameter that is modified again once the methodreaches step 108 in a subsequent cycle.

According to some embodiments of the invention as illustrated in FIG. 1,the mobile device's diversity signal may change gradually over time withmore precision, as compared to a system where the mobile device strictlycomplies with the base station's phase feedback signals. The calculationof the modified phase parameter value may be calibrated based on therecent behavior of phase feedback signals. For example, if more phasefeedback signals are similar than are different in a recent time period,the modified diversity signal may be calculated with smaller phase stepstoward a value indicated by a phase feedback signal. Conversely oralternatively, if phase feedback signals are more likely to differ froma succeeding phase feedback signal in a time period, the modifieddiversity signal may be calculated with larger phase steps toward aphase parameter value.

FIG. 2A is flowchart of a method of adjusting phase difference based oncomparing a current phase feedback with a prior phase feedback signal,according to an embodiment of the present invention. At block 202, amobile device may transmit an initial diversity signal using an initialphase parameter. At block 204, the mobile device may receive, from abase station, a current phase feedback signal meant to instruct themobile device to transmit the next diversity signal at an indicatedphase difference.

At block 206, the mobile device's processor may compare the currentphase feedback to a prior phase feedback signal received in a transmitcycle just before the transmit cycle of the current phase feedbacksignal. At block 208 a, if the current phase feedback is the same as theprior phase feedback signal, e.g., both phase feedback signals indicatea same value of a phase parameter, the mobile device's processor mayapply a phase step value to the initial value of a phase parameter in adirection towards the phase parameter of the current phase feedbacksignal. Applying a phase step value may include adding or subtracting aphase value. The phase step may be smaller than the difference betweentwo adjacently valued phase feedback signals. For example, if thepossible phase feedback signals from the base station differ by 90°, thephase step may predetermined to be 5°, 15°, 30°, 45°, or any other valueless than 90°.

At block 208 b, if the current phase feedback signal indicates adifferent value than the prior phase feedback signal, the modified phaseparameter value may be calculated as a midpoint value between the valuesof the current phase feedback signal and the prior phase feedbacksignal. For example, if a current phase feedback signal indicated aphase difference of 90°, and the prior phase feedback signal indicated aphase difference of 0°, the modified phase parameter may have a value of45°. The mobile device may then transmit a modified diversity signal atblock 210, using the calculated modified phase parameter value. Blocks204-210 may be repeated as more phase feedback signals are received fromthe base station.

FIG. 2B illustrates a series of closed-loop phase adjustments, accordingto an embodiment of the invention. A base station may, for example, havefour possible phase parameters to transmit in a phase feedback signal:0°, +90°, 180°, or −90°, as indicated in the legend as A, B, C, or D212. The mobile device may use a predetermined small phase step 214 of15°. A series of modified phase parameters 218 may be calculated basedon a series of phase feedback signals 216 from the base station. Eachfeedback cycle 220 may include a phase feedback signal received from thebase station, and a modified phase parameter value calculated by themobile device and transmitted in a diversity signal. The calculation ofthe modified phase parameter value may be based on the phase feedbacksignals received from the base station. It will be understood that thespecific values used in FIG. 2B are for illustration purposes, and thatother values may be used and calculated according to embodiments of theinvention. For example, a base station may have more or less than fourpossible phase parameters to transmit. The predetermined phase step maybe a different value other than 15°, such as 5°, 10°, 20°, 22.5°, or25°.

In feedback cycle 1, for example, the modified phase parameter maycomply with the base station's instructions, e.g., the mobile device maytransmit a first diversity signal with phase parameter of 0° uponreceiving first phase feedback signal of 0°. In feedback cycle 2, whenthe second phase feedback signal of +90° is transmitted to the mobiledevice, it is compared with the prior phase feedback signal of 0°. Sincethe second, or “current” phase feedback signal is different from thefirst phase feedback signal, the mobile device may calculate themodified phase parameter as a midpoint value between 0° and +90°,resulting in +45°. In feedback cycle 3, the third phase feedback signalof +90° is received, the mobile device will compare it with the second,or “prior” phase feedback signal received in feedback cycle 2. Since thethird and second phase feedback signal indicate the same value of aphase parameter, e.g., they both indicate +90°, the modified phaseparameter may be calculated by adding the small phase step of 15° to theprevious phase parameter transmitted at +45°. This results in a modifiedphase parameter indicating +60° for feedback cycle 3. In feedback cycle4, the fourth phase feedback signal may again indicate the same phaseparameter as the third phase feedback signal, and the small phase stepmay again be added to the previously calculated modified phase parameterof +60° in feedback cycle 3. This results in a modified phase parameterof +75° for feedback cycle 4. When the fifth phase feedback signal iscompared to the fourth phase feedback signal in feedback cycle 5, themobile device may determine that they indicate different values, e.g.,the fifth phase feedback signal indicates 0° and the fourth phasefeedback signal indicated +90°. The fifth modified phase parameter maybe calculated as the midpoint between the fourth and fifth phasefeedback signal, resulting in +45° for the modified phase parameter infeedback cycle 5. With each subsequent feedback cycle, the sameoperations of comparing phase feedback signals and calculating modifiedphase parameter based on the comparison may be repeated.

According to some embodiments of the invention, the mobile device mayhave additional or other constraints or controls in determining whetherand how to calculate a modified value of a phase parameter between thevalues of a current or most recent phase feedback signal and the valueof an initially transmitted phase parameter. For example, the mobiledevice may determine to calculate a modified value of the phaseparameter only if a plurality of consecutive phase feedback signals fromthe base station indicate the same phase value. In another example, asdescribed above in FIGS. 2A and 2B, the calculation may depend on acomparison between the current phase feedback signal and a prior phasefeedback signal. In yet another example, calculation may depend on aproportion of phase feedback changes that occur in a plurality of phasefeedback signals received in a time period, e.g., 50ms, 100ms, or 1s.Additional or other controls or comparisons may be performed before themobile device enters a phase adjustment mode or determines anappropriate method of calculation. According to some embodiments of theinvention, the mobile device may also perform other operations tocalculate the modified phase parameter, in addition to the operationsdescribed in FIGS. 1, 2A, and 2B. For example, the mobile device maymultiply a fraction to the difference in value between a currentfeedback signal and a prior feedback signal, and add the result to aninitially transmitted phase parameter. Other types or combinations ofmathematical operations may be performed in the calculation. It will beunderstood that the modified value may be between the initial phaseparameter value and the phase parameter indicated by a most recent phasefeedback signal, and the calculation of the modified phase value may bebased on the phase feedback signals from the base station or otherdiversity feedback received.

FIG. 3 is an illustration of a combination of control and calculationmethods for phase adjustment, according to an embodiment of theinvention. At block 302, the mobile device may first wait for a certainnumber of consecutive phase feedback signal indicating the same phaseparameter value, e.g., the mobile device may wait for six consecutivephase feedback signals indicating a phase parameter value of −90° orother value. Until then, the mobile device may transmit diversitysignals complying with phase feedback signals received from a basestation. Once a threshold number of consecutive identical phase feedbacksignals are received and the mobile device receives a different phasefeedback signal from the previous identical signals, the mobile devicemay enter into a phase adjustment mode at block 300.

A mobile device may transmit an initial diversity signal with an initialvalue of a phase parameter at block 304, and receive a current phasefeedback signal from a base station at block 306. The mobile device'sprocessor may then enter into a series of control loops to calculate anappropriate modified phase parameter value. At block 308, the currentphase feedback signal may be compared with a prior phase feedbacksignal. If both the current and prior phase feedback signals indicatethe same phase parameter value, the mobile device's processor maycalculate a modified phase parameter value by multiplying a constant toan average change in value of a plurality of phase feedback signals in atime period. The result may be added to the initial value of the phaseparameter at block 308 b. At block 314, the modified phase parameter maybe transmitted. The method may restart at block 306 when the mobiledevice receives a subsequent current phase feedback signal from a basestation. The modified phase parameter from the previous cycle may becomethe initial phase parameter transmitted with an initial diversitysignal.

At block 308, if the mobile device determines that the current and priorphase feedback signal indicates a different phase parameter value, themobile device's processor may determine a proportion of phase feedbackchanges among a plurality of phase feedback signals received in a timeperiod at block 310. At block 310, the proportion may be compared with athreshold proportion, and the calculation of the modified phaseparameter may be based on that comparison. Determining the proportion ofphase feedback changes that occur in a time period may involve comparingeach phase feedback signal in the time period to a succeeding phasefeedback signal, determining the number of phase feedback signals thatare different from a succeeding phase feedback signal, and then dividingby the number of phase feedback signals in said plurality of phasefeedback signals. The proportion may represent a probability that thephase feedback signal from a base station may change in future transmitcycles.

At block 310, the determined proportion may be compared with a thresholdproportion, and if the proportion is less than a threshold proportion,e.g., the likelihood that phase feedback signals will changedramatically is lower, then the mobile device's processor may calculatea modified micro phase parameter value by multiplying a fraction to thedifference in value between the current feedback signal and a priorfeedback signal. The resulting phase step may be added to the initialvalue of the phase parameter towards a same direction indicated by thephase feedback signal so that the modified phase parameter value isbetween the value of the received phase feedback signal and the value ofthe initial phase parameter. At block 314, the calculated modified phaseparameter may be transmitted with a modified diversity signal. If thedetermined proportion is greater than a threshold proportion at block310, the modified phase parameter may comply with the current phasefeedback signal at block 310 b.

In some embodiments of the invention, other control blocks may be usedthat are different from the control blocks illustrated in FIG. 3, or thecontrol blocks of FIG. 3 may be in a different order. For example, block308 and 310 may be in a different order, or another control block may bebetween them, leading to another calculation block determining amodified value of a phase parameter.

In some embodiments of the invention, the mobile device may continue tomonitor and compare the phase feedback signals received from the basestation. For example, after each transmission of a modified diversitysignal with a modified phase parameter, or after a period of timetransmitting using the modified phase parameter, blocks 304-312 may berepeated. The mobile device may receive further phase feedback signalsor other diversity feedback from the base station. Prior to calculatinga further modified diversity signal, the mobile device's processor mayagain compare phase values of successive phase feedback signals receivedfrom the base stations, for example.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

What is claimed is:
 1. A method of transmitting a diversity signal by amobile wireless communication device, comprising: transmitting aninitial diversity signal using an initial value of a phase parameter;receiving a current phase feedback signal from a base station indicatinga current value of the phase parameter; determining to calculate andthen calculating a modified value of the phase parameter, said modifiedvalue being between the initial value of the phase parameter and thecurrent value of the phase parameter; and transmitting a modifieddiversity signal using said modified value of the phase parameter,wherein calculating the modified value of the phase parameter comprises:comparing the current phase feedback signal to a prior phase feedbacksignal received from the base station, if the current phase feedbacksignal is the same as the prior phase feedback signal, then adding aphase step value to the initial value of the phase parameter in adirection towards the current value of the phase parameter, and if thecurrent phase feedback signal is different from the prior phase feedbacksignal, then calculating the modified value of the phase parameter as amidpoint value between the current value of the phase parameter and avalue of the prior phase parameter.
 2. The method of claim 1, whereindetermining to calculate a modified value of the phase parameter occurswhen a plurality of consecutive phase feedback signals received from thebase station are the same.
 3. The method of claim 1, further comprisingsaid steps of: determining a proportion of phase feedback changes amonga plurality of phase feedback signals received in a time period; anddetermining to calculate the modified value of the phase parameter basedon the proportion.
 4. The method of claim 3, wherein the step ofdetermining the proportion of the phase feedback changes among theplurality of the phase feedback signals received in the time periodcomprises: comparing each phase feedback signal in the plurality of thephase feedback signals to a succeeding one of the phase feedbacksignals, determining the number of the phase signals; and dividing by anumber of the phase feedback signals in the plurality of the phasefeedback signals.
 5. The method of claim 3, wherein determining tocalculate the modified value of the phase parameter comprises: comparingthe proportion to a threshold proportion; and when the proportion isless than the threshold proportion, then calculating the modified valueof the phase parameter.
 6. The method of claim 1, wherein calculatingthe modified value of the phase parameter comprises: multiplying afraction by the difference between the current value of the phaseparameter indicated by the current phase feedback signal and the valueof the prior phase parameter indicated by the prior phase feedbacksignal, resulting in the phase step; and adding the phase step to theinitial value of the phase parameter towards a same direction indicatedby the current phase feedback signal.
 7. The method of claim 1, whereincalculating the modified value of the phase parameter comprises:multiplying a constant by an average change in the current value of aplurality of phase feedback signals in a time period, resulting in thephase step; and adding the phase step to the initial value of the phaseparameter.
 8. A mobile communications device, comprising: a phasemodulator to produce an initial phase difference between two signalstransmitted on first and second antennas, based on an initial value of aphase parameter; a processor to: receive a current phase feedback signalfrom a base station, the current phase feedback indicating a currentvalue of the phase parameter; and calculate a modified value of thephase parameter by comparing the current phase feedback signal to aprior phase feedback signal received from the base station, if thecurrent phase feedback signal is the same as the prior phase feedbacksignal, then adding a phase step value to the initial value of the phaseparameter in a direction towards the current value of the phaseparameter, and if the current phase feedback signal is different fromthe prior phase feedback signal, then calculating the modified value ofthe phase parameter as a midpoint value between the current value of thephase parameter and a value of the prior phase parameter; and whereinthe phase modulator further produces a modified phase difference betweentwo signals transmitted on the first and second antennas, based on themodified value of the phase parameter.
 9. The mobile communicationsdevice of claim 8, wherein when a plurality of consecutive phasefeedback signals received from the base station are the same, themodified value of the phase parameter is then calculated.
 10. A mobiletransmit diversity system, comprising: a mobile communications device inuplink communication with a base station; and wherein: the mobilecommunications device transmits an initial diversity signal using aninitial value of a phase parameter; the mobile communications devicereceives transmit diversity feedback from the base station; the mobilecommunications device calculates a modified value of a phase parameterthat is between the value of the initial phase parameter and a currentvalue of the phase parameter indicated by a current phase feedbacksignal; and the mobile communications device transmits a modifieddiversity signal using the modified value of the phase parameter,wherein the mobile communications device calculates the modified valueof the phase parameter by comparing the current phase feedback signal toa prior phase feedback signal received from the base station, when thecurrent phase feedback signal is the same as the prior phase feedbacksignal, a phase step value is added to the initial value of the phaseparameter in a direction towards the phase parameter of the currentphase feedback signal, and when the current phase feedback signal isdifferent from the prior phase feedback signal, the modified value ofthe phase parameter is calculated as a midpoint value between thecurrent value of the phase parameter and a value of the prior phaseparameter.
 11. The mobile transmit diversity system of claim 10, whereinthe mobile communications device calculates the modified phase parameteronce a plurality of phase feedback signals from the base station are thesame.